A turbine is known as a power generating device for obtaining a power by converting a kinetic energy of a fluid into a rotational movement. On a turbine blade cascade end wall of the turbine, a so-called “cross flow (secondary flow)” is generated from the pressure side of one turbine blade toward the suction side of the adjacent turbine blade.
In order to achieve the improvement of the turbine performance, it is necessary to reduce the cross flow and to reduce a secondary flow loss generated in association with the cross flow.
In the turbine which converts the kinetic energy of the fluid into the rotational movement, there is a trend to set the circumferential velocity of rotation of the turbine to a value higher than that in the related art to improve the performance of the entire turbine. In association with it, setting the outflow angle of blades to a larger angle in comparison with that in the related art is required. On the other hand, the secondary flow loss in association with the cross flow generally tends to increase with the increase of the outflow angle of the blades.
In order to reduce the secondary flow loss in association with the cross flow to improve the turbine performance, a configuration having recesses and projections formed on the turbine blade cascade end wall in nonaxisymmetry is known (for example, see Patent Citation 1).
In the turbine blades which generate a shock wave, for weakening the shock wave and improving the turbine performance, a configuration having a concave shaped end wall near the turbine throat is known (for example, see Patent Citation 2).
Patent Citation 1: Specification of U.S. Pat. No. 6,283,713
Patent Citation 2: Specification of U.S. Pat. No. 6,669,445